The effects of a very low caloric diet (VLCD) combined with endurance exercise (EE) or endurance exercise and progressive resistance training (EEPRT) will be studied to determine the effects on the body composition of morbidly obese adults. Forty adutls will be matich for age, sex, weight, and body composition and assigned to either EE or EEPRT. The VLCD is a commercial product containing 500 kcal/day with 50 gm protein, 79 gm carbohydrate, and 1 gm fat. The diet is supplemented with a multiple vitamin to assure complete nutritional requirements are met. Medical supervision will provide reasonable assurance relative to the health of the subjects. Cardivascular fitness will be determined by a progressive treadmill protocol to exhaustion. Oxygen consumption will be determined by open circuit techniques. Body composition will be determined by hydrostatic weighing (HW) at residual volume (RV) and total lung capacity non-submerged (TLCNS). Corcumferences will be obtained and used in regression analysis with HW at RV to derive an equation capable of predicting body fat in the morbidly obese. One reptition maximum (IRM) will be used on large muscle groups to assess strength and serve as the basis for prescribing progressive resistance. Endurance exercise will progress from 40 minutes/day to 90 minutes/day, four days/week. Progressive resistance training will be prescribed at 3 day/week at 70% IRM and progress to 80% IRM. Analysis of body composition data will allow comparision of HW at RV and HW at TLCNS to determine if HW at TLCNS appears to be viable alternative. Analysis of body composition data obtained from circumference will determine if a prediction equation may be generated to predict percent fat. The comparison of body composition data from HW at RV between EE ad EEPRT will determine if EEPRT adds additional proteins sparing to EE alone.